The DNA Sequencing Minicore Facility (MiniCore) is designed to provide investigators in the Division of Basic Science of the NCI with rapid processing of their DNA sequence samples. Our goal is to generate accurate data as rapidly and efficiently as possible. The facility consists of two ABI 377 Prism automatic DNA sequencers and associated computers, PCR machines and equipment. These machines are capable of reading up to 750 base pairs with 95% accuracy. A professional staff, assigned exclusively to the MiniCore, makes it possible to generate data almost as rapidly as could be expected with a dedicated machine in the investigator's laboratory. Thus we lessen the need for such dedicated machines, which results in significant savings for the Division. The facility accepts samples from any member of the Division of Basic Sciences. We currently list 259 active users from 22 laboratories. Usually the user does the sequencing reaction, but we also accept DNA samples for reactions by the MiniCore. By limiting the range of services we offer, we focus our operation and optimize performance. In the past 12 months we have processed 23498 samples, a 56.5% increase over the preceding year. Our average turnover time, however, has actually decreased from 1.17 to 0.68 days (i.e. the weighted average number of business days from sample submission to when the samples are electrophoresed - an extra day should be added to allow the data to be generated and sent to the user). The Division subsidizes the MiniCore's operating expenses. The actual per-sample cost to the Division, and the turnover time, are considerably better than can be obtained from external, commercial sources. We charge $8.50 for each sample electrophoresed. An additional $12.00 is charged for each sample submitted for reaction and electrophoresis. We also support several sequence analysis programs for both PC and MacIntosh computers. These programs are made available to our user community at no charge. Finally, we also interact with users for troubleshooting, and in the design and interpretation of experiments involving DNA sequencing